1. Field of the Invention
The present invention is generally directed to a method of and an apparatus for cutting a web or a sheet-material, and more particularly, to a method of and apparatus for sequentially cutting such a thin and lengthy material into a sheet of photographic printing paper or the like.
2. Description of the Prior Art
After an image has been printed by beams of printing light emerging from a light source in a printer, a thin and lengthy material (hereinafter referred to as a sheet-material) like printing paper on which images are formed is cut off for every image.
A process of cutting the sheet-material typically involves the use of a sheet-material cutting apparatus (a sheet cutter) equipped with a fixed cutting edge fixed to a frame and a movable cutting edge engaged with the former. More specifically, the sheet-material is fed in a spacing between the opposed fixed and movable cutting edges. The movable cutting edge engages with the fixed cutting edge to produce a shearing force by which the sheet-material is cut into a cut segment and a remaining portion. The sheet-material is consecutively cut off to predetermined lengths by the above-mentioned method of and apparatus for cutting the sheet-material.
There arise, however some problems inherent in the foregoing conventional sheet-material cutting method. For instance, if the remaining portion is left for a relatively long time after cutting the sheet-material, the remaining portion of the sheet-material near the top thereof is curled down. As a result, the top of the sheet-material is caught by the fixed cutting edge when cutting the paper once again. For this reason, the remaining portion of sheet-material is not smoothly fed in the spacing between the fixed and movable cutting edges opposite to each other, thereby causing a blockade, i.e., a so-called jam of the sheet-material.
The conventional sheet-material cutting apparatus has an additional problem in which as the movable cutting edge moves (in such a direction as to separate from the fixed cutting edge) after cutting the sheet-material, the top of remaining portion thereof tends to contact the movable cutting edge, with the result that the top portion is raised and turned up by a frictional force caused therebetween. Such being the case, when cutting the sheet-material next time, the remaining portion of sheet-material encounters the difficulty of entering the spacing between the fixed and movable cutting edges. In consequence, there is caused a problem of creating the blockade, viz., the jam of the sheet-material.
To cope with this, the spacing between the fixed cutting edge and the movable cutting edge is widened. This simple arrangement in turn leads to a reduction in cutting velocity because of a larger amount of movement of the movable cutting edge, or to an increase in force required for driving the movable cutting edge.
Where the movable cutting edge serves as one side of a printing frame (easel) suited to print an image on the printing paper, a guide such as a plate for holding the sheet-material can not be disposed just in front of the movable cutting edge, i.e., on the up-stream side of a direction in which the sheet-material is carried.